Generally, in the course of generating a downmix signal by downmixing an audio signal including a plurality of objects into a mono or stereo signal, parameters (information) are extracted from the objects. Theses parameters (information) are used for a process for decoding a downmixed signal. And, pannings and gains of the objects can be controlled by a selection made by a user.
However, objects included in a downmix signal should be appropriately controlled by a user's selection. When a user controls an object, it is inconvenient for the user to control the object in direct. And, it may be more difficult to restore an optimal status of an audio signal including a plurality of objects according to an environment than to be controlled by an expert.